1. Field of the Invention
The present invention relates to an electric assisted bicycle which uses motor output as assistant motive power.
2. Description of the Related Art
An electric assisted bicycle, which carries out assist cycling by use of motor output during flat road and uphill runs, is provided with a battery as a power source of a motor. However, naturally there is a limit to distance run per electric charge, so that the expansion of mileage is greatly desired.
To respond to the desire, Japanese Patent Laid-Open Publication No. 2001-213383 (hereinafter called prior invention), for example, discloses invention in which the rotation of a wheel during applying a brake regeneratively generates electric power, and the battery is charged by regenerative current. In the prior invention, the rotation of a motor drive section is transmitted to the rear wheel via a one way clutch such as a ratchet mechanism or the like, and direct coupling means directly couples the one way clutch in response to the bias of brake means for braking the rear wheel.
Generally in a case where the one way clutch is interposed between the wheel and the motor, torque is transmitted from the motor to the wheel during cycling assisted by the motor, but the direction of torque transmission is reversed and torque is transmitted from the wheel to the motor under braking, so that the one way clutch idles. Without devising any measure, the torque is not transmitted to the motor and electric power cannot be generated in this state. In order to solve this problem, a friction clutch unit is provided in the above prior invention as direct coupling means, in which frictional force transmits the torque from an output side to an input side by means of pressing a clutch plate (denoted by the reference numeral 86 in the patent publication) against a member on the output side and a member on the input side.
Using this type of direct coupling means, however, complicates structure, because another clutch unit becomes necessary in addition to the one way clutch. Also, the friction clutch unit lacks the stability and reliability of operation due to its frictional structure.